1.1 Study area

Khor Al-Zubair canal is an extension of the Persian-Arabian Gulf waters in the lower reaches of Mesopotamia (Figure 1). It has a length of approximate 42 km, and a width of 1km at low tide, with an average depth of 10~20 m. In 1983, this water body was connected to an oligohaline marsh (Hor Al-Hammar,), by the Shatt Al-Basrah Canal, changing the environment of lagoon of the Khor from a hypersaline to an estuary (Hussain and Ahmed, 1999).

Figure 1 Sampling sites, indicating the position of the Khor Al-Zubair in the northern part of the Arabian Gulf

2 Results

In this study specimens of 13 species from two location in Iraqi coast of seven Brachyuran crabs families including, Macrophthalmidae, Portunidae, Pilumnidae, Ocypodidae, Camptandriidae, Varunidae and Sesarmidae (Brachyura) were observed and collected with abundant numbers (Table 1).

2.1 Systematics

Order: Decapoda Latreille, 1802. Superfamily: Xanthoidea MacLeay, 1938. Sub Family: Pilumnidae Samouelle, 1819. Family: Pilumninae Samouelle, 1819 (Figure 2A); Pilumnopeus convexus Maccagno, 1936 (Figure 2B).

2.1.1 Material examined

Carapace measurements are length (CL) × breadth (CB) mm, respectively.

Total 18 specimens (11 males and 7 females) collected during 2016.

In 10/3/2016 were five males (15.5 × 21.4), (16.9 × 24.2), (17.5 × 25.3), (18.5 × 26.2), (19.8 ×27.6) mm. and three females (16.5 × 25.8), (16.2 × 24.7), (17.4 × 25.7) mm.

In 24/12/2016 were six males(7.5 × 14.3), (9.6 × 14.8), (11.7 × 16.5), (13.4 × 19.9), (17.9 × 24.8), (17.1 × 25.6) mm, and four females (7.4 × 12.1), (8.3 × 13.6), (12.4 × 17.1), (16.8 × 24.5) mm. Collected by hand under rocks during lower tidal.

2.1.2 Description

Carapace smooth, broader than long (Figure 2A). Dorsal surface with rows of small rounded granules along transverse cristae on frontal, gastric and branchial regions, covered with scattered plumose setae of varying lengths mainly along transverse carapace ridges, never completely obscuring surface. Anterolateral margin with 3 teeth behind exorbital angle; first anterolateral tooth blunt, second and third teeth acute but not spine-tipped.

The chelipeds are unequal in both the sexes (Figure 2A). In larger specimens, the large chela appears to be smooth, very minute granules are present on ischium, merus carpus and outer surface of propodus. All the walking legs are with short and long plumose setae; smaller chela covered with fine granules and scattered short setae.

The abdomen (Figure 2B) is seven segmented, all the segments are clearly marked, both the margins are fringed with thickly plumose setae, and sparse plumose setae on the surface of the abdomen are also visible. The first gonopod (Figure 2B) is strongly curved (S-shaped). The distal part is very strongly incurved.

2.1.3 Remarks

P. convexus (Maccagno, 1936), was originally described (but not figured) from two female specimens from Ethiopia (size not stated). The population of P. convexus (Maccagno, 1936) in this study seems to be large sized. The males were 19.8-27.6 mm long while females were17.4-25.7 mm. Cooper (1997) has mentioned two types of populations, one being larger from the mangrove area and the other smaller from the beach, male 12.5-18.0 mm, female 11.1-17.2 mm.

P. convexus is one of the most common species found in a variety of habitats along the intertidal coast of the Persian Gulf. Apel (2001) examined material recorded as P. vauquelini by Stephensen (1946) and Basson et al. (1977) from the Persian Gulf and identified them as P. convexus. Apel (2001) believed that P. vauquelini does not occur in the Persian Gulf. He mentioned four morphologic characters allowing distinguishing these two closely related species (Apel, 2001).

2.1.4 Distribution

Distribution: Red Sea, Persian Gulf (Barnard, 1955) And now for the first time from Khor Al-Zubair, far of Northern of Arabian Gulf. The specie was recorded from sandy beach and under the rock in shores. The species is recorded from various habitats, such as mangroves, sandy beach and rocky shores.

2.3 Habitat

P. convexus collected from Khor Al-Zubair, found under artificial stones some under decaying wood, or under old boats at the intertidal zone.

Authors’ contributions

Both authors have contributed equally toward the publication of this paper.

Acknowledgments

We would like to thank the Marine Biology Department, Marine Science Center, Basrah University, Iraq for giving us the opportunity to examine and study the crabs specimens. Our thanks are also due to Dr. Talib A. Khalaf chef of Marine Biology Department, for reading the manuscript and for their valuable advice and suggestions.

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